The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

SA parliament to look into Hills bushfire

The South Australian parliament will investigate a recent bushfire in the Adelaide Hills which destroyed more than 600 hectares of scrub after the close of the fire season.

The Cherryville fire burnt for two days in early May during a period of unseasonably warm weather, almost two weeks after the end of the official bushfire season.

It started when a controlled fire in some leaves by a local property owner got out of control.

An upper house select committee already investigating community safety and emergency services will now be extended to cover the Cherryville blaze.

Opposition Leader Steven Marshall says the committee will look into how the fire started, evaluate the effectiveness and deployment of the fire fighting resources and consider the length of the fire danger season.

"We need to understand how we can better deal with situations like these, particularly in the heat of summer," Mr Marshall said.